This article is concerned with the knowledge of sea ice as developed and transmitted by the Inuit of Igloolik (Nunavut, Canada). The information on which this article is based was obtained from travelling, observation, and interviewing carried out from October 2000 to May 2001 in Igloolik, as well as several existing interviews from the Igloolik Oral History Project database. Inuit knowledge of sea ice reveals a deep understanding of the complex relationships between ice, currents, the Moon, and the winds, as well as a holistic approach to knowledge where classification based on a western scientific approach becomes difficult, if not counter-productive. Through detailed knowledge of ice topography, sea ice becomes a familiar territory for the Inuit of Igloolik, and, through the understanding of the ‘codes’ of the moving ice, its changing nature becomes predictable. This article does not pretend to give a full account of a system of knowledge the understanding of which requires a lifetime of practice and observation. However, it describes some of its elements and offer some insights regarding this complex aspect of Inuit Qaujimajatuqangit (Inuit knowledge, also known as IQ).